OBJECTIVES: Major emphasis is placed upon the study of tumor antigens of the transplantation rejection type (TSTA) and of the immune responses they evoke. As a corollary to this study, the biologic properties in vitro and in vivo of histocompatibility (H-2) antigens are under study. Solubilization and methods of purification of both TSTA and H-2 are under investigation with the ultimate purpose of defining these membrane antigens in physicochemical, biologic and molecular terms.